In general, a transmission properly changes driving force of a vehicle depending on driving condition, and it also has a gearing system to drive the vehicle backward because an engine does not counter rotate.
FIG. 1 schematically illustrates a cross-sectional view of an internal structure of a general manual transmission.
As shown in FIG. 1, the general manual transmission has a transmission operating structure to operate the switching state, and the structure includes: a gear lever directly operated by a driver; a shift rail 20 transferring the operating power of the gear lever to a gearshift; and a shift fork 10 operating a synchronizer sleeve 30 by connecting to the shift rail 20. Particularly, the shift fork 10 is fixed to the shift rail 20, and it has a structure of pushing and moving the synchronizer sleeve 30 to the axial direction as being inserted into a groove manufactured on the outer circumference surface of the synchronizer sleeve 30.
The synchronizer sleeve 30 is a component of a synchro-mesh device that is manufactured to make the gearshift easily geared. When a driver operates the gear lever, the shift fork 10 is operated through the shift rail 20, and then the synchronizer sleeve 30 moves back and forth by the shift fork 10.
Accordingly, as the synchronizer sleeve 30 moves back and forth by the operation of the gear lever, the synchro-mesh device works as a clutch, performs synchronizing action to make the main shaft and the shifting gear be the same speed by frictional force at the same time, and then connects a driving gear 40 side and a main shaft 50 side to complete shifting.
Herein, the shift fork 10 has a structure that an arm is formed to a semicircle shape and the arm is settled to the outer circumference surface of the synchronizer sleeve 30. Pad parts are installed in both ends of the inside of the arm to make the gear lever easily attached to the synchronizer sleeve 30, when the synchronizer sleeve moves back and forth by the operation of the gear lever.
During a manual transmission, since the shifting gear pushes the synchronizer sleeve 30 rotating at several thousands rpm, loads are concentrated to the pad part of the shift fork 10. Thus, it is necessary to improve wear resistance and low friction lubrication characteristics of a driving part such as the shift fork 10 to improve life time thereof and to provide competitiveness in vehicle fuel efficiency and emission control.
In the related arts, conventional methods for manufacturing a shift fork, for example, a Korean conventional art entitled “Die casting method of shift fork for vehicle, have been introduced. The methods may improve wear resistance and reduce the production cost by forming an aluminum/alumina thick layer (coating layer) on the contact site of the shift fork to the sleeve. However, when forming a coating layer by cold spray coating method, an amorphous coating layer may not be formed sufficiently, and wear resistance and low friction lubrication characteristics may not satisfy standards thereof.
The description provided above as a related art of the present invention is just for helping in understanding the background of the present invention and should not be construed as being included in the related art known by those skilled in the art.